Intraoperative 'non-lifting' peripheral nerve action potential recording

Abstract

The present invention is directed to an electrode system for recording nerve action potential (NAP) from surgically exposed nerve and methods for using such an electrode system. Electrophysiological methods are used during repair surgery of peripheral nerve trauma (PNT). PNT is a major medical problem with an annual incidence similar to that of epilepsy. Surgical intervention is provided based on the severity of nerve injury which is determined preoperatively and intraoperatively mainly by electrophysiological assessments. Among those, intraoperative nerve action potential (NAP) or compound action potential (CNAP) recording is preferred for direct assessment of functional continuity of the nerve.

1 . A system for stimulation or recording of a compound nerve action potential comprising:
 an elastic base, having at least three projections, wherein at least one of the at least three projections is positioned on a top side of a nerve and at least two of the at least three projections are positioned on a bottom side of the nerve, such that the nerve is sandwiched by the at least three projections;   an electrode for stimulation or recording of a nerve action potential comprising at least two metal contacts;   wherein the elastic base and the electrode are self-insulating and self-holding, such that a non-lifting nerve action potential can be stimulated and/or recorded.   
     
     
         2 . The system of  claim 1  wherein a middle projection and two outer projections comprise insulation that covers all of the middle projection and the two outer projections except for an area of the metal contact for nerve stimulation or recording. 
     
     
         3 . The system of  claim 1  further comprising the elastic base being formed from one selected from a group consisting of a plastic or silicone. 
     
     
         4 . The system of  claim 1  wherein a pressure is applied to the nerve because it is sandwiched by the at least three projections and wherein the pressure is less than what would be damaging to the nerve for a duration of a test of the compound nerve action potential. 
     
     
         5 . The system of  claim 1  wherein the at least three projections comprise grooves at a location of the electrode contact with the nerve, such that the nerve is self-positioned on the grooves. 
     
     
         6 . The system of  claim 1  wherein the projections can be opened by applying pressure to the elastic base using fingers or a surgical tool. 
     
     
         7 . The system of  claim 1  wherein the elastic base returns to its original shape after a deformation. 
     
     
         8 . The system of  claim 1  further comprising a device for applying deformation force to the elastic base. 
     
     
         9 . The system of  claim 1  wherein the elastic base is configured such that an application of deformation force to the elastic base releases pressure on the nerve. 
     
     
         10 . The system of  claim 1  wherein the elastic base is configured such that an application of deformation force allows the elastic base to be repositioned. 
     
     
         11 . The system of  claim 1  further comprising an impedance monitor. 
     
     
         12 . The system of  claim 11  wherein the impedance monitor measures impedance in real time. 
     
     
         13 . The system of  claim 11  wherein the impedance monitor couples the electrode to a neural stimulator device. 
     
     
         14 . The system of  claim 11  wherein the impedance monitor comprises a light emitting diode (LED). 
     
     
         15 . The system of  claim 14  wherein the LED is configured to indicate whether the electrode has a good connection to the nerve. 
     
     
         16 . The system of  claim 11  wherein the impedance monitor further comprises a switch, wherein the switch can be engaged to convert the electrode from stimulation and recording mode to impedance monitoring mode. 
     
     
         17 . The system of  claim 11  wherein the impedance monitor is configured to deliver short voltage pulses through the electrode. 
     
     
         18 . The system of  claim 11  wherein the impedance monitor further comprises an op-amp. 
     
     
         19 . The system of  claim 18  wherein the op-amp measures output from a voltage divider. 
     
     
         20 . The system of  claim 11  wherein a low impedance measurement indicates the electrode is shorted through saline in the body and a high impedance measurement indicates that the electrode is not connected.